铜陵地区高钾钙碱系列侵入岩

HIGH-POTASSIUM CALC-ALKALINE INTRUSIVE ROCKS IN TONGLING AREA, ANHUI PROVINCE

铜陵地区侵入岩在化学性质上不属于一般的钙碱系列岩石。它们可能是幔源碱性玄武岩浆同化古老麻粒岩相下地壳为主的酸性组分，同时发生结晶分离（ＡＦＣ的产物。铜陵地区侵入岩的特点是：以石英二长闪长岩为主，高钾富碱，富Ｓｒ，δＥｕ＝０９±。ε（Ｎｄ）和Ｉ（Ｓｒ）较低，Ｐｂ同位素比值中等，但均有较好的线性关系。在δ（Ｎｄ）─Ｉ（Ｓｒ）图和（２０７）ｐｂ／（２０４）ｐｂ─（２０６）ｐｂ／（２０４）ｐｂ图上，样品投影点的特点是均作陡倾斜排列。

The Mesozoic intrusive rocks in Tongling area are in high-K calc-alkaline rocks. They are formed by AFC (assimilation and fractional crystallization)mixing mechanism. The characteristics of the intrusive rocks in Tongling area are:high-K and alkali-riched,Sr-riched, lower ε(Nd), Rb/Sr and I(Sr), medium Pb isotopic ratio.There are fairly good liner correlation with steep incline between ε(Nd) and I(Sr),and (207)pb/(204)pb and (206)pb/(204)pb, showing that the mantle source magma had been contaminated by ancient lower-crust of granulite facies. The alkaline basaltic magma of mantle origin intruded into lower crust of about 26 km deep and assimilated acid composition under～1100℃ with crystallization of pyroxene,amphibole, magnetite and apatite (olivine) at the same time, and intruded up to shallow crust later. Petrology and Nd, Sr, Pb isotopes indicate that there exists Archean lower crust of granulite faces in Tongling area.